Pumps and painting installations

ABSTRACT

A pump assembly which is particularly suitable for supplying liquid to a direct pressure spray gun (i.e., an &#39;&#39;&#39;&#39;airless&#39;&#39;&#39;&#39; spray gun which does not require additional air to atomize such liquid) has pumping cylinder and piston members which deliver the liquid in response to alternating relative movement of the piston member axially within the cylinder member. One of these members, preferably the piston member, has a connection for engagement by a driving element such as an eccentric driven by an electric motor. The other member, preferably the cylinder member, is connected to a supporting element or chassis through a resilient connecting attachment which is prestressed to resist relative axial movement of such other member when the pumping pressures are within the desired range. The resilient attachment permits such relative axial movement, however, to a greater or lesser extent, when the pumping pressures exceed the desired range. Thus the other member moves, at times, more or less as a unit with the alternatingly driven member of the pump, to reduce or stop the pumping flow at such excessive pressures. A preferred resilient attachment includes an outer pressure control cylinder within which the pump cylinder body is supported for limited axial movement by two axially movable annular control pistons. Controlling pressures are established by a hydraulic circuit which includes the zone between the control pistons and a pressure accumulator which controls the prestressing of the resilient attachment.

[4 June 11, 1974 United States Patent [191 Schouteeten et al.

[ PUMPS AND PAINTING INSTALLATIONS airless spray gun which does notrequire additional air to atomize such liquid) has pumping cylinder andpiston members which deliver the liquid in response to alternatingrelative movement of the piston member axially within the cylindermember. One of these members, preferably the piston member, has aconnection for engagement by a driving element such as an eccentricdriven by an electric motor. The other member, preferably the cylindermember, is connected to a supporting element or chassis through aresilient connecting attachment which is prestressed to resist relativeaxial movement of such other member when the pumping pressures arewithin the desired range. The resilient attachment permits such relative3 a 4 S 7 mm m3 t-I 2 4 e MB 74 ,7 wmm .m 4Mw4 a i m M 4 M a I 4 e8 .E 27 e fi l 2 8 0 7 m a m w "4 ad we u H mm um .m n mun M ""4 de 9 9 u, nfie l m AUC n i "m" J l 5 7 U." at 2 m m 2 7 mmm Md m a t 0 mmh 0 r. m 0"ac c a 1" & m Q m r v 0 e N .l .f t n CIO n g 11 C 6 e P .l v S nu P ME11. l. 1 ll] 5 3 2 l 2 8 7 7 2 2 555 .l. [rt [ll axial movement,however, to a greater or lesser ex- [56] References cued tent, when thepumping pressures exceed the desired UNITED STATE range. Thus the othermember moves, at times, more S PATENTS or less as a unit with thealternatingly driven member of the pump, to reduce or stop the pumpingflow at such excessive pressures.

A preferred resilient attachment includes an outer pressure controlcylinder within which the pump .r nSe hwerm C s e awm FPBMH 0 cylinderbody is supported for limited axial movement by two axially movableannular control pistons. Primary Examiner-William L. Freeh Controllingpressures are established by a hydraulic circuit which includes the zonebetween the control Attorney, Agent, or Firm-Dorsey, Marquart,Windhorst, West & Halladay pistons and a pressure accumulator whichcontrols the prestressing of the resilient attachment.

11 Claims, 4 Drawing Figures PATENTEDJUM 1 m4 Pressure p A Curve ofpower limlt available In the pump (Motor power corrected) Maximumpressure of the pump Flow Maximum flow of pump PUMPS AND PAINTINGINSTALLATIONS BACKGROUND OF THE INVENTION Direct pressure sprayingpumps, i.e., those which are suitable for spraying liquid to a directpressure socalled airless" spray gun which does not require additionalair to atomize the liquid must meet a variety of different conditions.These pumps must operate under different running conditions. They shouldbe operable within a work range as wide as possible, including thepossibility of obtaining high pressures at very low flow rates, as wellas high flow rates at rather low pressures. Such pumps should also beadaptable as part of a light weight spray apparatus which is readilyportable, and which can be used with readily available power supplies.

The desired range of running conditions can be rather easily met, whenalternating stroke pneumatic motors are used to drive a paint supplypump, but the problem becomes difficult to solve when a mechanicallydriven pump isto be connected to an electric motor, which is necessarywhen the pump units are to be used in small private building yards orplants where compressed air is not readily available. In such cases itis necessary on the one hand to limit the weight of the installation inorder for it to be easily carried from one place to another. Thisconsequently reduces the permissible size of the electric motor. On theother hand, this type of use also limits the power to be used, since theelectric power available in private building yards and shops isgenerally low enough to place resulting limits on the motor power to beused.

It is possible to meet the above-stated variety of operating conditionsby using an electric motor in which the speed may be varied, but thissolution is far too expensive. It is also possible to meet the differentrunning requirements by using a pump construction in which the length ofthe piston stroke may be varied. However, it is not practical to varysuch piston strokes by modifying the radius of the driving eccentric,because this involves too heavy a construction, which is not acceptablefor a portable unit.

SUMMARY OF THE INVENTION In order to solve these problems in anacceptable manner, the present invention provides a suction and deliverypump with piston and cylinder members which are relatively movable withrespect to each other in alternating pumping strokes. One of thesemembers has a connection for engagement and movement by an alternatingdriving element for the pump, such as an eccentric on a rotary shaft.Between the other member and a suitable supporting element for it, theinvention provides a resilient attachment or connection which isprestressed in both directions to resist relative movement of themember. Thus, when the pumping pressures within the cylinder member arewithin a desired range, the resilient attachment will completely resistrelative movement between the supporting element and the member which itsupports, while the other member reciprocates back and forth at thenormal stroke length provided by the driving eccentric.

Preferably, the arrangement is such that the piston member is positivelyand directly connected to the driving eccentric, whereas the cylindermember is connected to the supporting element through the resilient orelastic attachment.

In this particular arrangement, when the pumping pressures within thecylinder member exceed a desired predetermined pressure range, theprestressing of the resilient connection is overcome to permit relativemovement of the cylinder member, in the preferred case, with respect tothe supporting element. Thanks to this feature of construction, when thepressure in the pump reaches the level of the prestressing or constraintprovided by the elastic attachment, the assembly made up of the pumpbody or cylinder and the pump piston can move together as a whole, thusovercoming the preconstraint of the elastic support attachment. Theresult is that the pump stops delivering liquid to the spray unit. Thepreconstraint is calibrated at a precise predetermined value, whichconsequently limits the pressure provided by the pump to the desiredpressure range, which may also be very precise.

The preferred form of elastic attachment or connection is one in whichtwo annular pistons can slide axially within the space between the outersurface of the pump cylinder and an inner cylindrical surface of thesupporting element. Each of the surfaces has two axially spaced stopswhich limit the extent to which the two annular pistons can be separatedfrom each other along either of the cylindrical surfaces. The annularspace between these two annular pistons is filled with pressurized fluidin a manner which resiliently urges the annular pistons away from eachother and against the stops on both the pump cylinder and supportingelement, to hold the pump cylinder stationary within the supportingelement when the pumping pressures are within the desired range. Thepressurized fluid within the annular space between the annular pistonsis provided in such a manner that the pistons can be moved toward eachother to a greater or lesses extent, when the pressure within the pumpcylinder exceeds that within the annular control space and tends to movethe pump cylinder with the pump piston member more or less as a unit.

The preferred construction also has a connection between the annularpressure control chamber located between the annular pistons and asuitable pressure accumulator, into which the pressurized fluid withinthe pressure regulating chamber may be forced when the pressure withinthe pump cylinder is greater than that within the pressure controlchamber. The invention further provides a one way flow control deviceand a pressure variation damping system in the connection between theaccumulator and the pressure control chamber.

Some of the advantages which can be expected in the use of pumpsconstructed according to this invention are as follows:

a. The construction limits the power actually consumed by the pump andconsequently limits the size of the motor which is necessary to drivesuch a pump.

b. The arrangement limits the pressure at the pump outlet, whether thespraying none is closed or open.

c. The device allows optimum use of the performance characteristics ofthe pump driving motor, by using to the best possible extent a workingzone which is made possible by the particular motor power curve.

d. The construction can be easily calibrated within a wide range ofpressures and delivery flow rates suitable for the material being usedand for the particular applications of the material to be sprayed. Inparticular, for painting applications, these pressures need to be welldefined in order to obtain correct spraying at the noz- .zle. Thus theinvention also makes possible an improved painting installation, whichincludes a pump of the improved construction defined above.

Other features and advantages of the invention will be better understoodfrom the following description and the attached drawings which show adirect pressure airless spraying installation as one illustration, butnot a limiting example, of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS of the apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENT The direct pressure (i.e., highpressure airless) spraying installation according to a preferredembodiment of this invention is shown generally in FIGS. 1 and 2 andincludes a special pump assembly 1 driven by an electric motor 2 whichhas a speed reducer 3 driving an eccentric 4. The installation includesa paint strainer 5 at the end of a hose 6, for insertion in a suitablesupply reservoir or container of liquid to be sprayed. The installationalso includes a spray gun 7 connected with the outlet opening of thepump by a flexible hose 8, through a suitable filter 11 and pressuregauge 12. The improved pump assembly of this installation also includesa hydro-pneumatic assembly 15, shown in more detail in FIG. 3, and thewhole pumping assembly is supported by a chassis or supporting frame 17on wheels 18.

The special pump assembly 1 is an alternating stroke suction anddelivery pump which includes a pump cylinder 21 (details of which areshown in FIG. 3), a bottom cylinder head 22 with a suction valve 23therein, and a piston 24 with a delivery valve 25, the end of the pistonrod 26 (sometimes called displacement rod) being coupled with eccentric4 (FIGS. 1 and 2) on shaft 28, which consists of an extension of theoutput shaft of the speed reducer 3.

To provide the desired elastic or resilient connection between the pumpcylinder and the suitable supporting element according to the invention,the pump cylinder may slide, with close engagement, within two axiallyspaced annular pistons 31 and 32 (FIG. 3). These pistons, in turn, aresupported for axial sliding movement within an outer cylinder 33, thusproviding an annular hydraulic control chamber 48 which is furtherdescribed below. The supporting cylinder 33 serves as the axially fixedsupporting element for pump cylinder 21. This cylinder 33, however, mayswing on a shaft 35 (made in this case as two spaced shaft portions, oneat each side of the pump cylinder axis) parallel to the shaft 28 of thepump driving eccentric 4. These shaft portions 35 are supported by ahollowed-out bed plate 36 rigidly connected or integral with chassis 17.The pump cylinder suction orifice is shown at 38, connected with inletstrainer 5 by hose 6. The outlet orifice from the pump cylinder is shownat 39 and is appropriately connected to the point spray gun 7 throughhose 8, as described. Shaft portions 35 permit the cylinder to swinglaterally (but not axially) to accommodate the lateral movement ofpiston rod 26 by eccentric 4.

The two annular or ring pistons 31, 32 of the resilient attachment, canslide axially both over the cylindrical external surface of the pumpcylinder body 21 and within the internal cylindrical face of thehydraulic control chamber cylinder 33, to allow the pump body cylinder21 to be driven axially back and forth within cylinder 33. The distancebetween the two ringpistons 31 and 32 is limited on the pump cylinder 21by two shoulders 43, 44 and in the control chamber 33 by two othershoulders 45, 46. The axial distance between the two shoulders 43, 44 isequal to the axial distance between shoulders 45 and 46.

Thus the sides of the two ring pistons 31, 32 which face each other, thebore of control chamber cylinder 33, and the cylindrical outer surfaceof pump body cylinder 21 form a closed control space 48, which istightly sealed by O-rings 51, 52, 53 and 54 mounted in the correspondingannular grooves in the internal and external cylindrical surfaces ofthese annular pistons.

This annular pressure control space 48 is connected through an opening57 in the wall of control cylinder 33 with a pipe 58 which extends intothe hydropneumatic assembly 15.

The hydro-pneumatic assembly 15 includes a pressure accumulator 61, adevice 62 for controlling the flow of oil, an oil reservoir 63, adischarge valve 64 and a pump-damper device 65 connected with reservoiror tank 63 by a three-way valve cock 66.

Pressure accumulator 61 is of a spherical type and is divided by aflexible membrane 71 into two compartments 72, 73. The first compartmentis fitted with an inflation valve 74 and contains compressed air, whilethe second compartment contains oil and is connected to the pipe 58through the intermediate pipe 76 and the oil flow controlling device 62.

The device 62 for controlling the flow of oil includes a valve 77 whichpermits the free passage of the oil in pipe 58 toward the accumulator61, the flow of oil in the opposite direction being restrained by itspassage through a conduit 78 which serves as a bypass around valve 77and is provided with a calibrated restricting orifice formed in thisexample by a pin-cock 79. Thus device 62 is an adjustable one-way flowrestraining device.

Oil tank 63 includes an air freeing or venting orifice 81 and two lowerorifices 82, 83 connected respectively with the discharge valve 64 andwith a three-way valve 66. The relief or discharge pressure of thedischarge valve 64 may be adjusted by means of a screw 86 in such amanner as to limit the pressure within compartment 73 of the accumulatorto which the discharge valve is connected, the excess oil being returnedto reservoir 63 through an outlet pipe 87 of the discharge valve.

The damping pump 65 includes a hollow piston 91 moving within a cylinder92 which is in communication with the pipe 58 connected to the hydrauliccontrol chamber 48 within cylinder 33. The force exerted by the oil onpiston 91 is balanced on the other face of the piston by a calibratedspring 94. The assembly is made in such a way that when there is nopressure, the spring is not preconstrained. This system forms a damperfor the variations in oil pressure within the hydraulic pressureregulating chamber 48.

This assembly is completed by elements which permit it to play,moreover, the part of an auxiliary pump for pressurizing the circuit.For this purpose, a hollow piston 95 of smaller diameter, which isintegral with the damping piston 91, works as a ram or plunger in asecond chamber 97 equipped with a suction valve 98 connected with theorifice 83 of oil reservoir 63 through the three-way valve or cock 66.The piston 95 is itself fitted with a valve 99 for driving back the oilinto the pipe 58 connected to the hydraulic compensation chamber.

On the three-way cock 66 is also connected a pipe 102 for connectionwith a source of oil under pressure.

The operation of the assembly of this installation is as follows:

Pump 1 is a double-acting pump. The amplitude of stroke of its piston 24is determined by the radius of eccentric 4, and the principle ofregulation consists in reducing or annuling the relative displacement ofthe piston with respect to the body (cylinder member) of pump 21 byallowing the latter to partially or completely follow the movement ofthe piston according to the pressure within the pump.

The accumulator 61 is initially inflated through valve 74 to a startingpressure Pi. The volume of air in compartment 72 of the sphere is thenequal to the total volume of the sphere.

The hydraulic circuit is then filled with oil at a pressure lower thanPi, through the suction valve 98 of the auxiliary pump 65, the three-waycock 66 and the pipe 102.

The annular control space 48 reaches its maximum pressure value inresponse to the effect of the pressure of the injected oil. Annularpistons 31, 32 are respectively in engagement with the stops 43, 45 and44, 46.

The whole circuit is purged with the aid of suitable devices.

A new quantity of oil is fed into the circuit under a pressure greaterthan Pi and penetrates into chamber 73 of the sphere, which leads to anew value Vo of the air volume in compartment 72 of the sphere. VolumeV0 is selected as a function of the desired characteristics. It must begreater than the volume generated by the displacement of one of theregulating pistons 31 or 32 along a length equal to the eccentricradius.

A pressure Po common to both the enclosed air and the hydraulic circuitcorrespond to this new volume Vo.

The outside oil feeding system 102 is disconnected and the suction valve98 of the auxiliary pump 65 is put into communication with the outlet 83of oil tank 63 through the cock 66.

In the following explanations, the main circuit will mean the assemblyconsisting of the control chamber 48, the sphere 61 and the connectingtube 58, 76 which directly connect them.

The following symbols also have the meaning indicated:

S: Effective area of pistons 31, 32 in the control chamber.

F,=POS

When the pump is put in operation, the force exerted on the bottom ofthe pump cylinder by relative downward movement of the piston is:

In a first assumption, if the pressure in the pump is such that:

F, F p P0 S/s then the pump body 21 is held in its position by theannular pistons 31, 32. The pump piston describes, relative to the pumpbody, a maximum travel or stroke. Thus one has the operating conditionsfor maximum delivery of fluid.

On the graph which shows pressures plotted against delivery or flowrates for this device (See FIG. 4), this operation at maximum flow rateis represented by a straight line segment AB parallel to the axis of thepressures.

The two ends of the segment are:

its meeting point A with the axis of flow or discharge rate, whichcorresponds to a null pressure with a maximum flow or delivery; and

point B which corresponds to the pressure:

In a second hypothesis, the pump outlet is closed. Since this is avolumetric pump, the pressure increases at once, and the piston and thepump cylinder body can then be considered as a rigid element connectedwith the rod-crank system. The control pistons 31 and 32 then describe,within the control chamber, strokes equal to the radius of theeccentric. Control piston 31 reaches its maximum stroke at the lowestpoint of the eccentric, and piston 32 at the highest point of theeccentric.

At these points, the volume of oil generated by the displacement of thepiston v S e (e being the radius of the eccentric) is forced into theoil compartment 73 of the sphere 61, thus reducing by the sameproportion the air volume, whose value becomes V, V0 v. The air pressureisthen P, P0 Vo/Vo v and the pressure of the liquid in the pump is P, P,S/s.

On the graph of pressures v. flows for the apparatus, a point C isobtained (p P (Q 0) corresponding to operation of the unit at a O or nilflow.

In a third assumption, the pump is discharged into a system in which thepressure drops are such that the pressure p reaches a value Whenpressure in the hydraulic circuit is lower than p P 8/5 the forceexerted by the annular piston 31 in engagement with the stop 43 andopposing itself to the downward movement of the pump body 21 is lowerthan the force exerted by the piston 24 of the pump on this same pumpbody (this latter force results from the pressure inside of the pumpbody). The result is that the relative stroke of pump piston 24 withrespect to the pump cylinder body 21 is temporarily annulled and isreplaced by an equal stroke of the regulating piston 31 in the controlchamber.

When the volume of oil forced out of the annular control space 48 of thecontrol chamber andinto the sphere 61 by means of this stroke reaches avalue such that P ps/ S the force holding the control piston 31 issufiicient, the displacement of the pump body 21 disappears, and therelative movement of the pump piston 24 with reference to the pumpcylinder 21 reappears, giving a new start to the flow rate.

In the course of this stage of operation, the relative stroke of thepump piston with respect to the pump body is a partial stroke, whichcauses a partial flow.

Curve D, which corresponds to operation of the unit at a partial flow,is a line whose ends are at points B and On the graph, the zone whichrepresents all the possible operating conditions of the pump is thus thezone B defined by the segments AB, BC and the portions A and OC of theaxes of the graph.

Finally, the curve M of the graph represents the ultimate power curveavailable from the pump, i.e., the power of the motor, taking intoaccount the total output of the installation.

The one-way flow restraining device 62 has the objective of limiting thepressure in the control chamber 48 during return movement of the controlpistons 31, 32 after they have passed top and bottom dead-centers of theeccentric, thus reducing to a considerable extent the efi'ects ofreversal of the direction of work on the eccentric and on the speedreducer.

The damping device 65 for pressure variations, which is located betweenthe control-chamber 48 and the oneway flow retarding device 62, isdesigned for damping the shocks between the stops and control pistons31, 32. In effect, when one of the control pistons ends its stroke inthe control chamber to return into engagement with a stop of the controlchamber, the opposite stop of the pump comes to rest against the otherpiston. Without a clamping device, the pressure in the control chamberwould change bluntly from the low pressure defined by the one-way flowcontrolling device to the pressure within the sphere 61. Since piston 91of the damping system rests against the spring 94 without preconstraint,variations in volume are produced at low pressures.

By absorbing the volume of oil displaced by the starting portion of thestroke of control piston 31, the damping system 65 delays the opening ofvalve 77 of the flow restraining device 62 and allows a gradual increaseof pressure up to the value of the pressure in the sphere 61.

This system is even more adaptable when the diameter of piston 91 issubstantial and the spring 94 flexible.

This system also offers the advantage of incurving the operating orrunning curve in the same direction as the motor power curve M.

Mechanical damping devices against shock may, in addition, beadvantageously located between the various stops and control pistons.

The auxiliary oil pump incorporated in assembly 65 provides forincreasing the pressure of the circuit by injecting into it oilcontained in the reservoir 63. The pump is operated by movement of thedamping piston 91 and then works continuously when the apparatus isrunning at a partial or null flow.

The adjustable discharge valve 64 serves to regulate the level ofdesired pressure within the circuit. Excess oil is sent back to the tank63.

It will be understood that the invention is not limited to the specificmode of carrying it out which is described and shown, and that manymodifications may be made according to the particular applicationsexcepted, without departing from the heart of the invention.

We claim:

1. A high pressure airless paint spraying installation including asuction and delivery pump comprising a pump piston member and a pumpcylinder member within which the pump piston member defines at least onepumping chamber having inlet and outlet passages, said pump piston andpump cylinder members being relatively movable with respect to eachother in alternating strokes along a predetermined axis to providepumping pressures in the pumping chamber within a desired high pressurerange, one of said pump members having a driving connection forengagement and movement of that member in opposite directions along saidaxis by an alternating driving element for the pump, a supportingelement for normally holding the other of said pump members at a fixedposition along said axis, and a resilient attachment between thesupporting element and the other of said pump members, said resilientattachment being prestressed to resist relative movement of the other ofsaid members along said axis with respect to the supporting element whenthe pumping pressures within the pumping chamber are within the desiredrange, but permitting such relative movement of the other of saidmembers along said axis with respect to the supporting element andthereby reducing the relative axial alternating movement of the pumppiston with respect to the pump cylinder when the pressures in thepumping chamber exceed the desired range, said resilient attachmentincluding a pressure control chamber separate from said pumping chamberand a pressure control system connected to said pressure control chamberand maintaining a predetermined control pressure therein.

2. A suction and delivery pump particularly useful for high pressurespray installations which do not require additional air, said pumpcomprising a pump piston member and a pump cylinder member within whichthe pump piston member defines at least one pumping chamber having inletand outlet passages, said pump piston and pump cylinder members beingrelatively movable with respect to each other in alternating strokesalong a predetermined axis to provide pumping pressures in the pumpingchamber within a desired high pressure range, one of said pump membershaving a driving connection for engagement and movement of that memberin opposite directions along said axis by an alternating driving elementfor the pump, a supporting element for normally holding the other ofsaid pump members at a fixed position along said axis, and a resilientattachment between the supporting element and the other of said pumpmembers, said resilient attachment being prestressed to resist relativemovement of the other of said members in each direction along said aixswith respect to the supporting element when the pumping pressures withinthe pumping chamber are within the desired range, but permitting suchrelative movement of the other of said members in each oppositedirection along said axis with respect to the supporting element andthereby reducing the relative axial alternating movement of the pumppiston with respect to the pump cylinder when the pressures in thepumping chamber exceed the desired range.

3. A suction and delivery pump particularly useful for high pressurespray installations which do not require additional air, said pumpcomprising a pump piston member and a pump cylinder member within whichthe pump piston member defines at least one pumping chamber having inletand outlet passages, said pump piston and pump cylinder members beingrelatively movable with respect to each other in alternating strokesalong a predetermined axis to provide pumping pressures in the pumpingchamber within a desired high pressure range, one of said pump membershaving a driving connection for engagement and movement of that memberin opposite directions along said axis by an alternating driving elementfor the pump, a supporting element for normally holding the other ofsaid pump members at a fixed position along said axis, and a resilientattachment between the supporting element and the other of said pumpmembers, said resilient attachment being prestressed to resist relativemovement of the other of said members along said axis with respect tothe supporting element when the pumping pressures within the pumpingchamber are within the desired range, but permitting such relativevmovement of the other of said members along said axis with respect tothe supporting element and thereby reducing the' relative axialalternating movement of the pump piston with respect to the pumpcylinder when the pressures in the pumping chamber exceed the desiredrange, the resilient attachment including two annular pistons supportedto slide axially in close engagement between two cylindrical co-axialsurfaces, one of which is associated as part of the supporting elementand the other of which is associated as part of that pump member whichis connected to the supporting element, limiting stops with eachcylindrical surface to limit the relative axial movement of the annularpistons, the annular pistons and cylindrical surfaces defining anannular pressure control chamber separate from said pumping chamber, anda pressure control system connected to said pressure control chamber andmaintaining a predetermined control pressure therein.

4. A pump according to claim 2 in which one of the two coaxialcylindrical surfaces is an external cylindrical surface of the pumpcylinder member, and the other coaxial cylindrical surface is aninternal cylindrical surface of the supporting element, which therebyprovides at least part of a housing for the control chamber.

5. A pump according to claim 4 having a main frame, a motor-drivenrotary driving shaft with an eccentric thereon, the piston member havinga rod connected to the eccentric, and the supporting element beingpivotally supported on the main frame for swivelling movement on an axisparallel to the rotary driving shaft.

6. A pump according to claim 3 in which the pressurized fluid is aliquid, and the pressure control system includes a pressure accumulatorhaving a movable partition dividing the accumulator into a pressurizedgas compartment and a pressurized liquid compartment, and a connectingfluid conduit between the control chamber and pressurized liquidcompartment.

7. A pump according to claim 6 in which the connecting conduit betweenthe control chamber and pressure accumulator includes a flow controllingdevice having a one-way valve portion to permit free liquid flow fromthe control chamber to the accumulator and having a restricted returnpassage shunted around the valve for limiting the liquid flow in theopposite direction.

8. A pump according to claim 7, which also includes a pressure vairationdamping device having a damping chamber connected to the controlchamber, and a spring-loaded damping piston movable in the dampingchamber against its spring-loading in response to pressure increases inthe control chamber.

9. A pump according to claim 8 in which the damping device includes anauxiliary pump chamber, a pumping piston portion moving integrally withthe damping piston, a conduit having a discharge valve between theauxiliary pump chamber and damping chamber, an inlet suction valve inthe auxiliary pump chamber, a reservoir for hydraulic liquid, and aconnecting conduit between the auxiliary pump chamber inlet valve andthe reservoir.

10. A pump according to claim 9 in which the pressurized liquidcompartment of the pressure accumulator has an adjustably calibratedrelief valve with an outlet orifice connected to the reservoir.

11. A pump according to claim 9 in which the connecting conduit betweenthe auxiliary pump chamber inlet valve and the reservoir includes athree-way valve member for selective connection of the auxiliary pumpchamber to a supply of liquid under pressure.

1. A high pressure airless paint spraying installation including asuction and delivery pump comprising a pump piston member and a pumpcylinder member within which the pump piston member defines at least onepumping chamber having inlet and outlet passages, said pump piston andpump cylinder members being relatively movable with respect to eachother in alternating strokes along a predetermined axis to providepumping pressures in the pumping chamber within a desired high pressurerange, one of said pump members having a driving connection forengagement and movement of that member in opposite directions along saidaxis by an alternating driving element for the pump, a supportingelement for normally holding the other of said pump members at a fixedposition along said axis, and a resilient attachment between thesupporting element and the other of said pump members, said resilientattachment being prestressed to resist relative movement of the other ofsaid members along said axis with respect to the supporting element whenthe pumping pressures within the pumping chamber are within the desiredrange, but permitting such relative movement of the other of saidmembers along said axis with respect to the supporting element andthereby reducing the relative axial alternating movement of the pumppiston with respect to the pump cylinder when the pressures in thepumping chamber exceed the desired range, said resilient attachmentincluding a pressure control chamber separate from said pumping chamberand a pressure control system connected to said pressure control chamberand maintaining a predetermined control pressure therein.
 2. A suctionand delivery pump particularly useful for high pressure sprayinstallations which do not require additional air, said pump comprisinga pump piston member and a pump cylinder member within which the pumppiston member defines at least one pumping chamber having inlet andoutlet passages, said pump piston and pump cylinder members beingrelatively movable with respect to each other in alternating strokesalong a predetermined axis to provide pumping pressures in the pumpingchamber within a desired high pressure range, one of said pump membershaving a driving connection for engagement and movement of that memberin opposite directions along said axis by an alternating driving elementfor the pump, a supporting element for normally holding the other ofsaId pump members at a fixed position along said axis, and a resilientattachment between the supporting element and the other of said pumpmembers, said resilient attachment being prestressed to resist relativemovement of the other of said members in each direction along said aixswith respect to the supporting element when the pumping pressures withinthe pumping chamber are within the desired range, but permitting suchrelative movement of the other of said members in each oppositedirection along said axis with respect to the supporting element andthereby reducing the relative axial alternating movement of the pumppiston with respect to the pump cylinder when the pressures in thepumping chamber exceed the desired range.
 3. A suction and delivery pumpparticularly useful for high pressure spray installations which do notrequire additional air, said pump comprising a pump piston member and apump cylinder member within which the pump piston member defines atleast one pumping chamber having inlet and outlet passages, said pumppiston and pump cylinder members being relatively movable with respectto each other in alternating strokes along a predetermined axis toprovide pumping pressures in the pumping chamber within a desired highpressure range, one of said pump members having a driving connection forengagement and movement of that member in opposite directions along saidaxis by an alternating driving element for the pump, a supportingelement for normally holding the other of said pump members at a fixedposition along said axis, and a resilient attachment between thesupporting element and the other of said pump members, said resilientattachment being prestressed to resist relative movement of the other ofsaid members along said axis with respect to the supporting element whenthe pumping pressures within the pumping chamber are within the desiredrange, but permitting such relative movement of the other of saidmembers along said axis with respect to the supporting element andthereby reducing the relative axial alternating movement of the pumppiston with respect to the pump cylinder when the pressures in thepumping chamber exceed the desired range, the resilient attachmentincluding two annular pistons supported to slide axially in closeengagement between two cylindrical co-axial surfaces, one of which isassociated as part of the supporting element and the other of which isassociated as part of that pump member which is connected to thesupporting element, limiting stops with each cylindrical surface tolimit the relative axial movement of the annular pistons, the annularpistons and cylindrical surfaces defining an annular pressure controlchamber separate from said pumping chamber, and a pressure controlsystem connected to said pressure control chamber and maintaining apredetermined control pressure therein.
 4. A pump according to claim 2in which one of the two coaxial cylindrical surfaces is an externalcylindrical surface of the pump cylinder member, and the other coaxialcylindrical surface is an internal cylindrical surface of the supportingelement, which thereby provides at least part of a housing for thecontrol chamber.
 5. A pump according to claim 4 having a main frame, amotor-driven rotary driving shaft with an eccentric thereon, the pistonmember having a rod connected to the eccentric, and the supportingelement being pivotally supported on the main frame for swivellingmovement on an axis parallel to the rotary driving shaft.
 6. A pumpaccording to claim 3 in which the pressurized fluid is a liquid, and thepressure control system includes a pressure accumulator having a movablepartition dividing the accumulator into a pressurized gas compartmentand a pressurized liquid compartment, and a connecting fluid conduitbetween the control chamber and pressurized liquid compartment.
 7. Apump according to claim 6 in which the connecting conduit between thecontrol chamber and pressure accumulator includes a flow controllingdevice haVing a one-way valve portion to permit free liquid flow fromthe control chamber to the accumulator and having a restricted returnpassage shunted around the valve for limiting the liquid flow in theopposite direction.
 8. A pump according to claim 7, which also includesa pressure vairation damping device having a damping chamber connectedto the control chamber, and a spring-loaded damping piston movable inthe damping chamber against its spring-loading in response to pressureincreases in the control chamber.
 9. A pump according to claim 8 inwhich the damping device includes an auxiliary pump chamber, a pumpingpiston portion moving integrally with the damping piston, a conduithaving a discharge valve between the auxiliary pump chamber and dampingchamber, an inlet suction valve in the auxiliary pump chamber, areservoir for hydraulic liquid, and a connecting conduit between theauxiliary pump chamber inlet valve and the reservoir.
 10. A pumpaccording to claim 9 in which the pressurized liquid compartment of thepressure accumulator has an adjustably calibrated relief valve with anoutlet orifice connected to the reservoir.
 11. A pump according to claim9 in which the connecting conduit between the auxiliary pump chamberinlet valve and the reservoir includes a three-way valve member forselective connection of the auxiliary pump chamber to a supply of liquidunder pressure.